| 摘要 |
PURPOSE:To enable smooth switching of magnetic field by setting the field current references during switching and after switching through utilization of a field weakening signal held in a holding means when the field is switched during field weakening control. CONSTITUTION:During field control, terminal voltage feedback VFBK of a motor 7 is fed to an absolute value converter 8 in order to produce an absolute value, and a difference signal representing the difference between the terminal voltage feedback VFBK and a field weakening operation start voltage fed from a setter 9 is fed to a proportional integration type automatic field weakening circuit 10. Field weakening signal holding means 10, 12 for holding the field weakening signal prevailing before switching of field are provided, and field current references during switching and after switching are set through utilization of the field weakening signals held in the holding means 10, 12 when the field is switched during field weakening control. By such arrangement, proper field current reference IFREF can be ensured corresponding to the motor speed resulting in smooth switching of field. |
